It has long been realized that static mixers, if made to work efficiently, provide certain economical advantages over dynamic mixers for, as the name implies, static mixers employ no moving parts. As such, static devices are generally less expensive to configure and certainly much less expensive to maintain while providing the user with an extended useful life for the mixer product in service.
Prior art approaches to static mixers have generally involved expensive machining, molding, casting or other fabrication of the component mixer elements coupled with some type of permanent attachment between elements and a conduit and/or between elements within a conduit. The resulting costs and difficulty of manufacturing result in a relatively expensive end product. Moreover, many of the prior mixers provide less than complete mixing, particularly with respect to material flow along the walls of the conduit. This so called “wall smearing” is related to the parabolic velocity profile of a fluid in laminar flow with a fluid velocity approaching zero along the wall surfaces.
A marked improvement in static mixer technology was represented by the teachings of U.S. Pat. No. 3,923,288. The invention embodied in the cited patent was taught to be a stationary material mixing apparatus comprised of a plurality of self-nesting, abutting and axially overlapping elements which are fit into a conduit. Each region of axial overlap between elements provides a mixing matrix introducing complex velocity vectors into the materials. The mixing elements claimed in U.S. Pat. No. 3,923,288, the disclosure which is incorporated by reference, includes a flat central portion and first and second ears rounded or otherwise configured at their outside peripheries to fit within a conduit or within a cylindrical space. Such mixing elements induce a rotational angular velocity to fluids passing through them and when used with similar mixing elements can induce appropriate mixing as fluid streams interact with one another in a shearing matrix. In the case of a single input stream into an assembly of “n” such mixing elements, one obtains 2n divisions of the stream. This is so because each mixing element involves a 2×2 division of the flow stream.
A device capable of increasing the mixing efficiency of mixing elements such as those disclosed in the cited prior art to something greater than 2n divisions was disclosed in U.S. Pat. No. 4,614,440. In its broadest terms, the cited '440 patent taught a stationary material mixing apparatus for mixing a fluid stream which is in a shape of a conduit comprising individual biscuit sections. The sections were aligned along a common longitudinal axis, while each biscuit section comprised a plurality of openings therethrough, where within each of the openings were located mixing elements which induce the appropriate rotational angular velocity to the fluid stream. Substantially all of the mixing elements were taught to induce the same rotational side to the fluid noting that openings in adjacent biscuit sections were purposely misaligned to enhance the mixing operation.
It has now been determined that a much more highly efficient motionless mixing assembly can be fabricated within an appropriate conduit to increase mixing efficiencies well beyond those of the prior art.
These and further objects will be more readily apparent when considering the following disclosure and appended claims.